Not applicable.
1. Field of the Invention
The present invention relates to post-fermentation kettle hop essences and flavorants, and methods of making and using them. More particularly, it relates to glycosides which are capable of imparting kettle hop essence and flavor (e.g., aroma and taste) to malt beverages.
2. Background of the Art
Hops in brewing mainly add bitterness and impart a hop flavor (e.g., taste and smell) in the final product. Hops are composed of soft resins, hard resins, hop oils, waxes, lipids, and carbohydrates. The soft resins consist of xcex1-acids and xcex2-acids. The soft resins and a hop oil fraction are extractable by organic solvents, or by liquid and supercritical CO2. In conventional brewing, the xcex1-acids are converted into iso-xcex1-acids which are responsible for the bitterness taste. However, as the character of hop flavor is concerned, its description in beer is subjected to a great deal of debate, but all agree that the hop flavor (or the kettle hop flavor) is an essential part in the total organoleptic impact of beer.
When hops, hop extracts, or a hop oil fraction undergo boiling in wort, the hop oils (terpene and sesquiterpene hydrocarbons) are lost mostly through volatilization. As a result, these hydrocarbons are not found in most beers in significant amounts and therefore are not responsible for kettle hop flavor (V. Peacock and M. Deinzer, ACS Symp. Series 170:119-127, 1981). The surviving hop oil components include some oxidized hop oil compounds in very small quantities. We and other investigators have found that these oxidized compounds have very little effect on the kettle hop flavor (J. Irwin, Proc. Conv. Inst. Brew 20:99-104, 1988; Y. Fukuoka and M. Kowaka, Rep. Res. Lab. Kirin Brew. Co. 26:31-36, 1983).
Hops or a hop oil fraction have often been added after fermentation to maintain such volatile hydrocarbon flavors. This practice is called xe2x80x9cdry hoppingxe2x80x9d (J. G. Guzinski, The New Brewer pp. 19-21, July-August 1989; L. Narzixcex2, et al., Monatsschrift fur Brauwissenschaft 38(10):406-409, 1985). But these hop flavors are not considered to be a true and delicate xe2x80x9ckettle hop flavorxe2x80x9d. In the past, attempts have been made to separate hop oil components into various fractions with the purpose of adding these fractions to unhopped beer in order to achieve kettle hop flavor in the products thus produced. These attempts have all met with failure. We believe that the true xe2x80x9ckettle hop flavorxe2x80x9d refers to the flavor derived from other hop components either intact or modified during fermentation and not to these volatile or oxygenated hydrocarbons.
Heretofore, the brewer produces a different hopped wort stream for each finished beer product having the desired kettle hop flavor characteristics. This entails using dedicated equipment for each such wort stream. Thus, the brewer is faced with many production, quality control, and financial considerations especially when many different products must be produced.
Understanding the chemistry of kettle hop flavor would have a striking impact on the brewing process for quality and for economy. Our previous work utilizing the hop solids (the residue left when hops are extracted by either liquid/supercritical CO2 or non-polar organic solvents), or water extracts of hop solids, to achieve a kettle hop flavor in beer convinced us to investigate their composition and transformation. Our approach is different from that of the prior art by not focusing on the components in the volatilized hop oils or a hop oil fraction, but concentrating on the water soluble substances in hops or those water soluble substances remaining in the hop solids.
Thus, a need exists for understanding the chemistry of kettle hop flavor components. Such an understanding would allow the brewer to construct a kettle hop flavor essence which could then be added to an unhopped beer stream to obtain a beer with the desired degree of kettle hop flavoring.
We have discovered a new class of kettle hop flavor essences and flavorants which, surprisingly, can be added to an unhopped beer stream to achieve economy, flexibility, consistency, and quality to the brewing process.
One aspect of the invention provides a method of making a purified kettle hop essence and flavorant, comprising: extracting hops with an aqueous alcohol to produce an extract containing polar, water soluble compounds; concentrating the extract with respect to the polar, water soluble compounds; and purifying the concentrated extract with respect to kettle hop essences and flavorants to produce the purified kettle hop essence and flavorant. Preferably, the ratio of hops to aqueous alcohol is 1:1 to 1:100 w/v and the hops are hop solids. It is also preferred that the aqueous alcohol contains 0.1% to 100% v/v water and that the alcohol is ethanol. Preferably, the concentrating step is accomplished by evaporation.
The purifying step is preferably accomplished by the steps of (a) feeding the extract to a liquid chromatography column having a packing material selected from the group consisting of polymeric resins, activated carbon, molecular sieves, silica gels, derivatized silica gels, celluloses, and derivatized celluloses whereby kettle hop essences and flavorants are retained on the packing material; (b) eluting the kettle hop essences and flavorants from the packing material to obtain an eluent containing the compounds; and (c) further concentrating the compounds in the eluent by evaporation.
The purifying step can also be accomplished by the steps of (a) feeding the extract to a membrane process selected from the group consisting of filtration, reverse osmosis, ultrafiltration, size-exclusion, dialysis, electro-dialysis, and osmosis whereby the kettle hop essences and flavorants are retained in a retentate and (b) further concentrating the compounds in the retentate by evaporation.
It is especially advantageous if the above purification steps are directed to the removal of at least a portion of the free carbohydrates and inorganic salts from the extract.
Another aspect of the invention provides adding at least one hop fraction selected from the group consisting of hop oil, iso-xcex1-acids, dihydroiso-xcex1-acids, tetrahydroiso-xcex1-acids, and hexahydroiso-xcex1-acids to the above purified kettle hop essence and flavorant.
It is advantageous that the kettle hop essences and flavorants are glycosides and that at least some of the glycosides are converted to aglycones by breaking the attachment of the sugar moiety to the aglycone. Such a converting step in the above methods can be accomplished in the presence of enzymes which are selected for their ability to break the attachment of the sugar moiety to the aglycone. Conversion can also be accomplished by fermentation in the presence of yeast and model wort; by fermentation in the presence of yeast and wort; or by acid hydrolysis.
A further aspect of the invention provides a kettle hop essence and flavorant comprising a purified aqueous lower alcohol extract of hops which has been purified with respect to kettle hop essences and flavorants. Preferably, the hops are hop solids, and the kettle hop essences and flavorants are glycosides. It is also advantageous that the essence and flavorant further comprises at least one hop fraction selected from the group consisting of hop oil, iso-xcex1-acids, dihydroiso-xcex1-acids, tetrahydroiso-xcex1-acids, and hexahydroiso-xcex1-acids.
A still further aspect of the invention provides a kettle hop essence and flavorant comprising a purified and converted aqueous alcohol extract of hops which has been purified with respect to glycosides and then at least partially converted by breaking the attachment of the sugar moiety to the aglycone molecule. Preferably, the hops are hop solids, and the essence and flavorant further comprises at least one hop fraction selected from the group consisting of hop oil, iso-xcex1-acids, dihydroiso-xcex1-acids, tetrahydroiso-xcex1-acids, and hexahydroiso-xcex1-acids.
Another aspect of the invention provides a method of making kettle hop flavored beverages from a fermentable growth media comprising the steps of: fermenting the media; and adding to the fermented media the essence and flavorant of the above kind to form the kettle hop flavored beverage. The method can include the further step of adding at least one hop fraction selected from the group consisting of hop oil, iso-xcex1-acids, dihydroiso-xcex1-acids, tetrahydroiso-xcex1-acids, and hexahydroiso-xcex1-acids.
Yet another aspect of the invention provides a method of making a kettle hop flavored beverage from a fermentable growth media comprising the steps of: adding to the media, prior to fermentation, the essence and flavorant; and fermenting the media to form the kettle hop flavored beverage. The method can include the further step of adding at least one hop fraction selected from the group consisting of hop oil, iso-xcex1-acids, dihydroiso-xcex1-acids, tetrahydroiso-xcex1-acids, and hexahydroiso-xcex1-acids.
Another aspect of the invention provides a kettle hop flavored beverage prepared by methods of the above kind.
A still further aspect of the invention provides a kettle hop essence and flavorant comprising: linalool, xcex1-terpineol, ipsdienol, and geraniol, or precursors, or derivatives thereof. Preferably, the essence and flavorant is synthetically produced and substantially pure.
The objects of the invention, therefore, include providing kettle hop flavor essences (and methods of making and using them):
(a) which can be added directly to unhopped beer to impart a kettle hop flavor to the beer similar to conventional processes using whole hops or hop pellets in the kettle boil;
(b) which produce a light-stable beer product;
(c) which provide economy, efficiency, consistency, flexibility, convenience, and quality to the brewing process; and
(d) which increase capacity and flexibility with respect to brewhouse operations and the use of fermentation and aging tanks in the brewing process.
These and still other objects and advantages of the present invention will be apparent from the description below. However, this description is only of the preferred embodiments. The claims should, therefore, be looked to in order to assess the whole scope of the invention.